Interactions between bovine serum albumin and alginate: an evaluation of alginate as protein carrier

Determination of LMF binding site on a HSA-PPIX complex in the presence of human holo transferrin from the viewpoint of drug loading on proteins

Holo transferrin (TF) and the natural complex of human serum albumin and protoporphyrin IX (HSA-PPIX) are two serum carrier proteins that can interact with each other. Such an interaction may alter their binding sites. In this study, fluorescence spectroscopy, as well as zeta potential and molecular modeling techniques, have been used to compare the complexes (HSA-PPIX)-LMF and [(HSA-PPIX)-TF]-LMF. The Ka1, Ka2, values of (HSA-PPIX)-LMF and [(HSA-PPIX)-TF]-LMF were 1.1×10(5) M(-1), 9.7×10(6) M(-1), and 2.0×10(4) M(-1), 1.8×10(5) M(-1), respectively, and the n1, n2 values were respectively 1.19, 1.53 and 1.17, 1.65. The second derivative of the Trp emission scan of (HSA-PPIX)-LMF exhibited one negative band at 310 nm, whereas for the [(HSA-PPIX)-TF]-LMF system, we observed one negative band at 316 nm indicating an increase in polarity around Trp. The effect of TF on the conformation of (HSA-PPIX)-TF was analyzed using three-dimensional fluorescence spectroscopy. The phase diagram indicated that the presence of a second binding site on HSA and TF was due to the existence of intermediate structures. Zeta potential analysis showed that the presence of TF increased the positive charges of the HSA-PPIX system. Site marker experiments revealed that the binding site of LMF to HSA-PPIX changed from Sudlow's site IIA to Sudlow's site IIIB in the presence of TF. Moreover, molecular modeling studies suggested the sub-domain IIIB in HSA as the candidate place for the formation of the binding site of LMF on the (HSA-PPIX)-TF complex.

Addition of perfluorocarbons to alginate hydrogels significantly impacts molecular transport and fracture stress

Perfluorocarbons (PFCs) are used in biomaterial formulations to increase oxygen (O(2) ) tension and create a homogeneous O(2) environment in three-dimensional tissue constructs. It is unclear how PFCs affect mechanical and transport properties of the scaffold, which are critical for robustness, intracellular signaling, protein transport, and overall device efficacy. In this study, we investigate composite alginate hydrogels containing a perfluorooctyl bromide (PFOB) emulsion stabilized with Pluronic(®) F68 (F68). We demonstrate that PFC addition significantly affects biomaterial properties and performance. Solution and hydrogel mechanical properties and transport of representative hydrophilic (riboflavin), hydrophobic (methyl and ethyl paraben), and protein (bovine serum albumin, BSA) solutes were compared in alginate/F68 composite hydrogels with or without PFOB. Our results indicate that mechanical properties of the alginate/F68/PFOB hydrogels are not significantly affected under small strains, but a significant decrease fracture stress is observed. The effective diffusivity D(eff) of hydrophobic small molecules decreases with PFOB emulsion addition, yet the D(eff) of hydrophilic small molecules remained unaffected. For BSA, the D(eff) increased and the loading capacity decreased with PFOB emulsion addition. Thus, a trade-off between the desired increased O(2) supply provided by PFCs and the mechanical weakening and change in transport of cellular signals must be carefully considered in the design of biomaterials containing PFCs.

Enzymatically cross-linked alginic-hyaluronic acid composite hydrogels as cell delivery vehicles

An injectable composite gel was developed from alginic and hyaluronic acid. The enzymatically cross-linked injectable gels were prepared via the oxidative coupling of tyramine modified sodium algiante and sodium hyaluronate in the presence of horse radish peroxidase (HRP) and hydrogen peroxide (H2O2). The composite gels were prepared by mixing equal parts of the two tyraminated polymer solutions in 10U HRP and treating with 1.0% H2O2. The properties of the alginate gels were significantly affected by the addition of hyaluronic acid. The percentage water absorption and storage modulus of the composite gels were found to be lower than the alginate gels. The alginate and composite gels showed lower protein release compared to hyaluronate gels in the absence of hyaluronidase. Even hyaluronate gels showed only approximately 10% protein release after 14 days incubation in phosphate buffer solution. ATDC-5 cells encapsulated in the injectable gels showed high cell viability. The composite gels showed the presence of enlarged spherical cells with significantly higher metabolic activity compared to cells in hyaluronic and alginic acid gels. The results suggest the potential of the composite approach to develop covalently cross-linked hydrogels with tuneable physical, mechanical, and biological properties.

Combined organic-inorganic fouling of forward osmosis hollow fiber membranes

This research focused on combined organic-inorganic fouling and cleaning studies of forward osmosis (FO) membranes. Various organic/inorganic model foulants such as sodium alginate, bovine serum albumin (BSA) and silica nanoparticles were applied to polyamide-polyethersulfone FO hollow fiber membranes fabricated in our laboratory. In order to understand all possible interactions, experiments were performed with a single foulant as well as combinations of foulants. Experimental results suggested that the degree of FO membrane fouling could be promoted by synergistic effect of organic foulants, the presence of divalent cations, low cross-flow velocity and high permeation drag force. The water flux of fouled FO hollow fibers could be fully restored by simple physical cleaning. It was also found that hydrodynamic regime played an important role in combined organic-inorganic fouling of FO membranes.

Interaction between holo transferrin and HSA-PPIX complex in the presence of lomefloxacin: an evaluation of PPIX aggregation in protein-protein interactions

Human serum albumin (HSA) and holo transferrin (TF) are two serum carrier proteins that are able to interact with each other, thereby altering their binding behavior toward their ligands. During the course of this study, the interaction between HSA-PPIX and TF, in the presence and absence of lomefloxacin (LMF), was for the first time investigated using different spectroscopic and molecular modeling techniques. Fluorescence spectroscopy experiments were performed in order to study conformational changes of proteins. The RLS technique was utilized to investigate the effect of LMF on J-aggregation of PPIX, which is the first report of its kind. Our findings present clear-cut evidence for the alteration of interactions between HSA and TF in the presence of PPIX and changes in drug-binding to HSA and HSA-PPIX complex upon interaction with TF. Moreover, molecular modeling studies suggested that the binding site for LMF became switched in the presence of PPIX, and that LMF bound to the site IIA of HSA. The obtained results should give new insight into research in this field and may cast some light on the dynamics of drugs in biological systems.

Development and in vitro characterization of insulin loaded whey protein and alginate microparticles

Insulin was encapsulated into microparticles (MP) made of denaturized whey proteins (WP) and alginate (ALG) using an extrusion/cold gelation process with calcium ions. High encapsulation efficiency of 85% was obtained. Influence of insulin on polymeric viscosity and on microparticle behavior was evaluated. Insulin seemed to interact with WP chains by non covalent binding and steric hindrance. This influence was balanced by ALG addition. Nevertheless, insulin was released rapidly by diffusion at both acidic and intestinal dissolution media. Despite this fast in vitro release, WP/ALG MP showed an important enzymatic inhibition effect on trypsin and alpha-chymotrypsin. Thus, WP/ALG MP contributed to an effective insulin protection towards enzymatic degradation. The aforementioned results suggested that WP based microparticles are a promising carrier for improving oral delivery of insulin.

Impact of conditioning films on the initial adhesion of Burkholderia cepacia

Bacterial initial adhesion to inert surfaces in aquatic environments is mainly governed by the surface properties of the substratum, which can be altered significantly by the formation of conditioning films. Bacteria were tested for ability to adhere to bare glass slides and to slides coated with alginate, bovine serum albumin (BSA), or Suwannee River natural organic matter (SR-NOM). Three Burkholderia cepacia strains with different extracellular polymeric substance (EPS) secretion capacities were tested. The surface roughness of the slides was measured by atomic force microscopy (AFM), but its effect on bacterial initial adhesion was not significant. Our results showed the degree (number of cells per cm(2)) of initial adhesion among the three strains of B. cepacia was not significantly different, indicating that B. cepacia surface EPS did not impact adhesive capacity in the conditions tested. Depending on the conditioning film types and ionic strength conditions, conditioning film coatings can either enhance or reduce bacterial initial adhesion. Bacterial adhesion to bare slides and to alginate or SR-NOM coated slides increased with increasing ionic strength; however, a similar trend was not observed on BSA coated slides. Although BSA coated slides were the most hydrophobic and had the lowest negative surface charge among the surfaces tested, bacterial adhesion was not enhanced by the BSA coating. The extended Derjaguin-Landau-Verwey-Overbeek (DLVO) theory was applied to explain bacterial adhesion to solid surfaces.

Transport of biological molecules in surfactant-alginate composite hydrogels

Obstructed transport of biological molecules can result in improper release of pharmaceuticals or biologics from biomedical devices. Recent studies have shown that nonionic surfactants, such as Pluronic® F68 (F68), positively alter biomaterial properties such as mesh size and microcapsule diameter. To further understand the effect of F68 (incorporated at concentrations well above the critical micelle concentration (CMC)) in traditional biomaterials, the transport properties of BSA and riboflavin were investigated in F68-alginate composite hydrogels, formed by both internal and external cross-linking with divalent cations. Results indicate that small molecule transport (represented by riboflavin) was not significantly hindered by F68 in homogeneously (internally) cross-linked hydrogels (up to an 11% decrease in loading capacity and 14% increase in effective diffusion coefficient, D(eff)), while protein transport in homogeneously cross-linked hydrogels (represented by BSA) was significantly affected (up to a 43% decrease in loading capacity and 40% increase in D(eff)). For inhomogeneously cross-linked hydrogels (externally cross-linked by CaCl(2) or BaCl(2)), the D(eff) increased up to 50 and 83% for small molecules and proteins, respectively. Variation in the alginate gelation method was shown to affect transport through measurable changes in swelling ratio (30% decrease) and observable changes in cross-linking structure as well as up to a 3.6- and 11.8-fold difference in D(eff) for riboflavin and BSA, respectively. Aside from the expected significant changes due to the cross-linking method utilized, protein transport properties were altered due to mesh size restrictions (10-25 nm estimated by mechanical properties) and BSA-F68 interaction (DLS). Taken as a whole, these results show that incorporation of a nonionic surfactant at concentrations above the CMC can affect device functionality by impeding the transport of large biological molecules.

Repair of rat calvarial bone defects by controlled release of rhBMP-2 from an injectable bone regeneration composite

The objective of the present study was to enhance the regeneration ability of an injectable bone regeneration composite (IBRC) by the controlled release of recombinant human bone morphogenetic protein-2 (rhBMP-2). The IBRC comprised nano-hydroxyapatite/collagen (nHAC) particles in an alginate hydrogel carrier. First, bovine serum albumin (BSA) as a model protein was released from IBRC to evaluate its release rules. The results suggested that IBRC is a good controlled release carrier for BSA in the range 5-75 µg/ml. In the in vitro study the rhBMP-2 released from IBRC was determined by an enzyme-linked immunosorbent assay specific for rhBMP-2. The bioactivity of the released rhBMP-2 was evaluated through differentiated function of marrow mesenchymal stem cells (MSCs), as measured by alkaline phosphatase activity. The results of an in vitro study confirmed that rhBMP-2 released continuously for 21 days, and its bioactivity was well preserved during this period. The bone formation ability was assessed using a rat calvarial defect model of critical size. Micro-computed tomography (micro-CT) and histological analysis demonstrated that the IBRC had good bone formation ability, which was promoted through rhBMP-2 released from IBRC/rhBMP-2. In vitro and in vivo studies suggested that the present system is a potential bone critical defect repair material for clinical applications.

Structure and biocompatibility of an injectable bone regeneration composite

With the development of minimally invasive techniques, injectable materials have become one of the major hotspots in the biomaterial field. We have developed an injectable bone regeneration composite (IBRC) using calcium alginate hydrogel as matrix to carry nano-hydroxyapatite/collagen particles. In this work, we evaluated the homogeneity of IBRC by dry/wet weight ratio test. The results showed that the structural homogeneity was determined by controlling the molar ratios of trisodium phosphate to calcium sulfate rather than alginate concentration in the studied ranges. Pore sizes of wet IBRC samples were characterized by thermoporometry. The pore properties of dried IBRC were tested by mercury porosimetry. Average pore size and porosity of dried IBRC declined with increasing alginate concentration. In contrast, surprisingly, pore size of wet homogeneous IBRC increased with increasing alginate concentration. Meanwhile, the swelling ratio did not increase with varying alginate concentration, but the swelling degree increased with increasing alginate concentration. In vitro cell culture showed that IBRC had no obvious cytotoxic effect on the rat bone mesenchymal stem cells. The morphology and viability of cells were also related to MR value. IBRC had good histocompatibility with a mild short-term inflammatory response in rat dorsum muscle. In addition, the excellent ability of IBRC to promote bone healing was confirmed by 5-mm-diameter cranial defects using histological analysis and bone mineral density measurement.

Protective effects of kappa-ca3000+CP against ultraviolet-induced damage in HaCaT and MEF cells

In this study, the complex kappa-ca3000+CP combined collagen peptide with kappa-carrageenan oligosaccharide was tested for its ability to moderate UV-induced damage and investigated for its protective mechanism against UV radiation. Human keratinocytes (HaCaT) and mouse embryonic fibroblasts (MEF) were used to monitor the effects of kappa-ca3000+CP on cell viability, apoptosis, level of collagen I and MMP-1, MAPKs activation and intracellular ROS production after UV-irradiation. The results indicated that application of the kappa-ca3000+CP (100 microg/ml) could significantly attenuate UV-induced HaCaT and MEF death, as well as inhibit the UV-induced apoptosis of HaCaT cells. The decreased collagen I synthesis and the increased MMP-1 expression of MEF by UV radiation were almost restored back to normal level after treatment with kappa-ca3000+CP. Moreover, kappa-ca3000+CP could significantly suppress UV-induced MAPKs activation and intracellular ROS production. Taken together, these results showed that antioxidant property of kappa-ca3000+CP can effectively attenuate UV-caused cell damage and skin photoaging by suppressing cell apoptosis and expression of MMP-1 through the MAPKs signaling pathways. Thus, kappa-ca3000+CP has potential antiaging effects and prominent protective effects on UV-induced skin cell damages, which might be used in pharmaceutical and cosmetic industries.

Selection of an analytical method for evaluating bovine serum albumin concentrations in pharmaceutical polymeric formulations

Bovine serum albumin (BSA) is a commonly used model protein in the development of pharmaceutical formulations. In order to assay its release from various dosage forms, either the bicinchoninic acid (BCA) assay or a more specific size-exclusion high performance liquid chromatography (SE-HPLC) method are commonly employed. However, these can give erroneous results in the presence of some commonly used pharmaceutical excipients. We therefore investigated the ability of these methods to accurately determine BSA concentrations in pharmaceutical formulations that also contained various polymers and compared them with a new reverse-phase (RP)-HPLC technique. We found that the RP-HPLC technique was the most suitable method. It gave a linear response in the range of 0.5-100microg/ml with a correlation co-efficient of 0.9999, a limit of detection of 0.11microg/ml and quantification of 0.33microg/ml. The performed 't'-test for the estimated and theoretical concentrations indicated no significant difference between them providing the accuracy. Low % relative standard deviation values (0.8-1.39%) indicate the precision of the method. Furthermore, the method was used to quantify in vitro BSA release from polymeric freeze-dried formulations.